Instantaneous frequency analyzer



July 8, 1952 H. R. FosTER ETAL INSTANTANEOUS FREQUENCY ANALYZER Filed OCG. 8, 1949 Sums whvmow u r mirmrzu m\ Evo.

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Harry I?, FOSez' BY Efzzzo E. Crum/v ATTORNEY Patented July 8, 1952 INSTANTANEOUS FREQUENCY ANALYZER Harry R. Foster, East Orange, and Elmo E. Crump, West Caldwell, N. J., assignors to Ohmega Laboratories, Pine Brook, N. J.

Application October 8, 1949, Serial No. 120,394

9 Claims.

This invention relates to a system for instantaneously translating the f requency components of complex audio wave forms into dynamic visible characters which may be used for various purposes. Some of these purposes may be dened as follows, speech training and study thereof, for the education of the deaf, or vibration, analysis of noise measurements or for the production of cardiograms and the like for use in medical study.

It is therefore the principal object of our invention to provide an apparatus which will be highly useful as a translator of the wave forms heretofore mentioned.

Another object of our invention is to provide kwhat We term a Sonalator which will attain the principal object at a relatiyely low cost as compared with prior art structures directed to a similar class of work. Class systems have been built which analyze audio frequencies but these have been large and expensive systems that have been commercially impractical, so it is the further object of our invention to reduce the cost of our new system as Well as to reduce its size and Weight.

Our improved system includes an audio portion or a microphone or some noise producing structure and an audio amplifier, the response of which is essentially at from 50 to 4000 cycles per second. The system also includes a frequency analyzer structure with which is associated a carrier oscillator of 100,000 cycles per second, the purpose of which is to raise the audio frequency band from 50 to 4000 cycles, up to 100,050 cycles per second to 104,000 cycles per second. This frequency band is then amplified by the I. F. amplifier, the output of which is applied to a series of quartz crystal filters spaced 135 cycles apart. These crystals which we utilize are 29 in number and they cover a range from 100,135 cycles per second to 104,015 cycles per second. By utilizing this frequency the size of the quartz crystals become physically small and light weight, which is of advantage since, if conventional and audio frequencies are used, large and heavy component parts would be required. As will be later explained, in detail, the output of each crystal filter will be rectified in order to obtain a D. C. voltage in proportion to the amplitude of the signal passing through each crystal. After pass- 2 ing the crystal filters and rectiflers to get the D. C. voltage, the D. C. output of the rectiflers is carried to the grids of a rotary beam tube which corresponds to a commutating structure.

A beam of electrons is rotated and the output is taken from a common plate and carried to a cathode ray tube, the operation of which is regulated by a synchronizing pulse which comes from the rotary beam tube. A display is obtained on the cathode ray tube in which the horizontal direction denotes time and the vertical direction denotes frequency.

With this general description of our new and improved system, reference will now be made to the drawing in which Figure 1 illustrates the general system showing one display on the cathode ray tube.

Figure 2 illustrates another display on the screen of the cathode ray tube. M illustrates a pick-up or microphone, while A illustrates an audio amplifier having a range of 50 to 4000 cycles. U is a modulator which may or may not be used. O is a carrier oscillator which is connected intermediate the audio amplifier and the I. F. amplier I, when the modulator is not used, the output of which is connected to a plurality of crystals C, twenty-nine being indicated in steps of cycles from 100,135 c. p. s. to 104,015. After bypassing the crystals C, the current is passed through filters F including the resistances R and R1 the rectifier D and condenser C. These filters are connected to their respective grids G, I to 29 inclusive, of the rotary beam tube T.

Thus a D. C. voltage is proportional to the amplitude of the signal passing through each crystal. For example, assume that frequencies of 1000, 2000 and 3000 are present at the pick up or microphone., The frequencies at the output of the I. F. amplifier would then appear as 101,000, 102,000 and 103,000 cycles per second. This means that at grid 8 for example, there would appear a D. C. voltage, the amplitude of which would be proportional to the 1000 cycle note at the microphone. At grid I5 another D. C. voltage would appear which is proportional to the 2000 cycle note appearing at the microphone and at grid 22 a D. C. voltage proportional to the 3000 cycle audio note. In other Words, any complex frequencies appearing within the band 50 to 4000 cycles per second at the microphone would be broken up into frequency bands and will appear as D. C. voltages at the output of the rectiers which are made up of R, R1, D and C. It should be noted that with this arrangement the system is substantially instantaneous. Furthermore, it may be mentioned that systems in the past have been built which analyzed directly at audio frequencies; however, the size and cost of these prior systems which differ greatly in many ways from the system of this present application, renders them commercially impractical. The tube T is of the general type such as shown in Skellett Patent No. 2,433,403 issued December 30, 1947. The tube T has a relatively large circular plate P and a co-operative or spare grid 30 and plate P1 which is connected to the vertical sweep plates 3| of the cathode ray tube. The grid 30 and plate P1 act to deliver from the rotating beam tube T a pulse to synchronize the vertical deflection of the cathode ray tube beam. The grid 32 of the cathode ray tube is connected to a video ampliiier V that in turn is connected to the common plate P of tube T. The voltage in this circuit coming from the plate P determines the brightness on the screen of the cathode ray tube.

In the tube T, E is a plurality of elements which make up the eld electrode structure. These elements are positioned so that as the beam rotates the electrons will pass through the apertures 33 between these elements to the grids G which control the amount of energy passing to the common plate P.

The screen display shown in Figure 1 is that of a steady modulated tone.

The display shown in Figure 2 is that of a soprano voice showing vibrato.

These displays are relatively simple and have been chosen merely for ease in illustrating the principles involved in our invention.

From what has been said it will be understood that many of the details of the parts shown and described herein can be varied over a wide range without departing from the spirit of our invention and the scope of the appended claims. Having thus described our invention what we claim 1s:

1. An instantaneous frequency analyzing system including pick-up means, an audio amplifier connected to said means, a modulator and I. F. amplifier connected in series arrangement with the audio amplier and a carrier oscillator connected to the modulator, a plurality of crystals having different frequency detecting ability connected to the I. F. amplier, the crystals diering from each other over a relatively narrow range of cycles per second approximately as specified a single i'ilter means for each crystal output to deliver a D. C. voltage, a rotary beam tube having a plurality of grids each directly connected to its cooperative filter means to receive said D. C. voltage, a cathode ray tube to receive the output of said beam tube, and a synchronizing pulse pick-up on the rotary beam tube for controlling `the action of said cathode ray tube.

2. v A heterodyne system for audio analysis having a plurality of separate small crystal detectors to receive and separate a plurality of electrical impulses of different frequencies, the separation being of the order of approximately 135 cycles per second rectifying means for each crystal output, a rotary beam tube having a grid for each crystal and its rectifier and connected directly thereto for utilizing the output of each rectifying means and a cathode ray tube having vertical and hori- 4 zontal deflection plates connected to said rotating beam tube and displaying in order the signals picked up by said grids and received therefrom.

3. A system as defined in claim 2 further characterized in that a synchronous pulse is applied from the rotary beam tube to the vertical deflection plates of the cathode ray tube.

4. A heterodyne system for audio analysis having a plurality of separate small crystal detectors to receive and separate a plurality of electrical impulses of different frequencies, the separation being of the order of approximately cycles per second rectifying means for each crystal output, a rotary beam tube having grids, one for each rectifying means and directly connected thereto, the grids being arcuately spaced within the tube, a common circular plate in operative relation to all of said grids, a cathode ray tube having a grid connected to said circular plate through a video amplifier, and a synchronizing grid and plate in said rotary beam tube connected to the vertical deflector plates of the cathode ray tube through a vertical sweep generator.

5. A system as dened in claim 4 further charterized' in that the synchronizing grid and plate are arcuately located between the first and last grids connected to said rectifying means.

6. A heterodyne system for frequency analysis for frequencies up to approximately 200 kc. having a plurality of separate small crystal detectors to receive and separate a plurality of electrical impulses of different frequencies, the separation being of the order of approximately 135 cycles per second rectifying means for each crystal output for delivering a voltage having defined characteristics, a tube having a rotary electron beam and a plurality of arcuately arranged grids one for each rectifier circuit, means for directing said beam successively to each grid as the beam rotates, a circular plate operatively associated with said grids, a cathode ray tube having the usual grid, vertical and horizontal deilector plates, a horizontal sweep generator connected to said horizontal plates, a vertical sweep generator connected to said vertical plates, a synchronizing plate and grid in the rotary beam tube and connected to said vertical sweep generator and a video amplifier connected between said circular plate and the grid of the cathode tube.

'7. An electrical system as dened in claim 6 further characterized in that the vertical action is fast in the order of 1/250 of a second to traverse the display of the cathode ray tube as determined by the synchronizing pulse coming from the rotary beam tube, and further characterized in that a voltage which sweeps the electron beam is applied to the plates of the horizontal sweep at a relatively slow rate in the order of once in every. three seconds.

8. An electrical system as dei-med in claim 6 further characterized in that the frequencies applied to the crystal detectors range from approximately 100,000 to 104,000 cycles per second While the detectors are chosen and adjusted to select frequencies 135 cycles apart throughout this range of frequencies for passage to their respective rectiers for the purposes described.

9. A complex wave analyzing system especially adapted for use in the audio and supersonic spectra, including means for translating said waves to a much higher frequency range, means for analyzing said frequencies of the complex wave in this higher range, said last-mentioned means comprising a plurality of piezo-electric 5 crystals arranged to pass energy of a relatively small frequency separation as specified, a rectier for each crystal output and a rotary beam tube having grids connected one each directly to one of said rectiers, said tube having means for transmitting the impulses received by t to an indicating structure for producing visual pictures of said impulses.

HARRY R. FOSTER.

SRCH

UNITED STATES PATENTS Number Name Date 1,976,481 Castner Oct. 9, 1934 1,985,046 Marrison et al Dec. 18, 1934 5 2,433,403 skenett Dec. 30, 1947 2,476,445 Lacy July 19, 1949 OTHER REFERENCES Radio-Electronics, October 1948, pages 40, 41. l0

ELMO E. CRUMP.

REFERENCES CITED The following references are of record in the le of this patent:

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